Ja Morant just had one of the best jewelry shopping sprees ever -- he copped a bunch of expensive diamonds ... and then shot tequila with Gunna!!!
The fun time all went down at the Icebox jewelry store in Atlanta last week ... when the NBA star came to the famous showroom to get some of his old pieces cleaned up and to shop for more.
TMZ Sports has learned ... as the 22-year-old was browsing items -- they brought out Don Julio 1942, and everyone had a shot.